Tagging network elements simplifies network management.
What are Tags?
I wrote a blog a few years ago, Device and Interface Tagging, in which I described the use of tags to identify the purpose of various network elements. A tag of “TAG:core-core” would identify an interface that connects one core device to another core device. Adding “TAG:dist” to the device’s SNMP Location string would identify a distribution device without needing to include that string in the device name. (Including the device purpose in the name may still be a good idea to help us work with the network.) These tags would be used to aid in grouping within the network management system. Network management configuration automation can then use these tags to automatically identify devices and interfaces that should have a specific configuration change applied. During troubleshooting, it allows someone to quickly identify which links are performing a given purpose. Multiple tags can be used, up to the limit of the space available in the description field.
APIC Uses Tags!
I happily discovered this week that Cisco’s APIC (Application Policy Infrastructure Controller) provides for the use of tags on interfaces and devices. There are three short videos by Adam Radford on using the APIC REST API, and the second one describes setting the tag and location information for an interface and a device. Multiple tags can be applied, which makes them very useful. I don’t claim to have originated the use of tags, even though I came up with it independently. I’ve seen a few references to using tags after I came up with the idea and I am sure that I wasn’t the first.
APIC puts the tags to good use. The REST API allows a single configuration change to be applied to all elements that have a specified tag. Be careful, though. The REST API uses both “tag” and “scope” to reference a defined tag. The video I referenced above uses “tag”, while the Cisco Live session BRKCDN-2967 (San Francisco 2014), pp 37, uses “scope” to apply a QoS policy to all devices with the tag “branch”. (Note: It seems to me that the policy would be applied to interfaces, not devices, but since I’m just learning the REST API, I could very well be wrong.)
I’m happy about anything that improves our ability to manage networks. APIC’s tags and locations are a welcome addition that will be very beneficial.